1. Technical Field
This invention generally relates to an image forming apparatus, such as a copier, a printer, a facsimile machine, and a multifunction machine including at least two of coping, printing, facsimile transmission, plotting, and scanning capabilities.
2. Description of the Background Art
Conventionally, when a large number of sheets are continuously fed for a long time in electrophotographic image forming apparatuses, an image forming unit is continuously driven for a long time. Consequently, temperature inside the image forming apparatus and those of components thereof rise. Accordingly, various approaches have been tried for temperature control.
For example, there are image forming apparatuses that include a cooling fan or duct to prevent the temperature inside the image forming apparatus and those of the components from rising above a predetermined temperature, and there are high-speed image forming apparatuses that include an air conditioner to adjust temperature inside the apparatus.
Additionally, in image forming apparatuses in which temperature of a fixing roller locally rises due to continuous feeding of small sheets, the temperature of the fixing roller is directly monitored to temporarily increase the sheet feeding interval, thereby make the temperature of the fixing roller uniform.
Further, JP-2010-134407-A discloses an image forming apparatus aimed at suppressing excessive temperature rises of a developing motor without directly detecting the temperature of the developing motor. In this image forming apparatus, fluctuations in temperature of the developing motor is calculated based on the operation mode of the image forming apparatus, a power source off time during which a power source is turned off is estimated based on the change in temperature of a fixing thermistor, the fluctuations in temperature of the developing motor is corrected based on the power source off time, and an environment temperature is added to the corrected fluctuations in temperature of the developing motor to calculate the estimated temperature of the developing motor. When the temperature of the developing motor rises to 100° C. or higher, the image forming apparatus intermittently executes image formation in such a manner that the continuous image formation and standby in which image formation is not performed are repeated until the estimated temperature of the developing motor falls 80° C. or lower.
Further, JP-2006-251504-A discloses an image forming apparatus aimed at preventing firm adhesion of toner onto a toner regulating member when the amount of toner consumed is large. In the image forming apparatus, the number of toner images per dot formed on an image bearer is counted, and when the count value reaches a predetermined reference value or greater, a series of image formation is executed after stopping the rotation of a developing roller for a predetermined time, thereby cooling the toner layer on the developing roller.